20% of
the total energy consumed in developed countries is utilized for air-conditioning.
Thus, especially for
places experiencing warm and humid conditions, besides the huge energy bills
paid by the end-users, air-conditioning equipment is responsible for enormous
carbon emission. Thus, HVAC industry requires innovative solution which can
substantially boost the performance of air-conditioners. Hyper-efficient
dehumidifiers that can utilize the low-temperature heat that the condenser
otherwise rejects, need to be designed to completely eliminate the latent-heat
load on the evaporator and help make air-conditioners highly energy efficient.

Solution

NUS
researchers have developed a dehumidifier that can be easily
installed/retrofitted in the ducting, upstream of the air-handling unit (AHU)
of a conventional central air-conditioning unit as shown in Figure 1(a). The
dehumidifier is a bank of tubes that is coated with a solid-desiccant on its
external surface, see Figure 2. It realizes quasi-isothermal dehumidification
and regeneration processes (as opposed to adiabatic processes in conventional
desiccant wheels) which makes the dehumidification/regeneration process highly
efficient only requiring ultra-low grade heat for regeneration. As shown by the
process line in Blue in Figure 1 (b), it can completely handle the latent heat
load of outdoor air by utilizing (i) the room-return air as the regeneration
air-stream (ii) warm water at ~38 oC
from the water-cooled condenser during regeneration (iii) cool water at 30 oC from the cooling tower (or an auxiliary
water-condenser). Note that the air-states in Figures 1(a) and (b) are
consistent.